U.S. patent number 10,436,702 [Application Number 15/149,276] was granted by the patent office on 2019-10-08 for corrosion sensor, corrosion monitoring system, and method of quantifying corrosion.
This patent grant is currently assigned to GENERAL ELECTRIC COMPANY. The grantee listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Sundar Amancherla, Krishnamurthy Anand, Paul Stephen Dimascio, Rebecca E. Hefner.
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United States Patent |
10,436,702 |
Anand , et al. |
October 8, 2019 |
Corrosion sensor, corrosion monitoring system, and method of
quantifying corrosion
Abstract
A corrosion monitoring system includes at least one corrosion
sensor. The corrosion sensor includes a metallic plug having at
least one opening, at least one ceramic sheath in the opening of
the metallic plug, and a plurality of probes. Each probe has a
central portion with a predetermined cross sectional area extending
from the metallic plug. The ceramic sheath electrically isolates
each first end and each second end of the probes from the metallic
plug and the other first ends and second ends. The probes are sized
to provide a distribution of predetermined cross sectional areas of
the central portions. The corrosion monitoring system also includes
a resistance meter measuring an ohmic resistance for at least one
of the probes and a computer determining a corrosion rate by
correlating a rate of change of the ohmic resistance to the
corrosion rate of the probe.
Inventors: |
Anand; Krishnamurthy
(Karnataka, IN), Dimascio; Paul Stephen (Greer,
SC), Amancherla; Sundar (Dhahran, SA), Hefner;
Rebecca E. (Fountain Inn, SC) |
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
(Schenectady, NY)
|
Family
ID: |
58672424 |
Appl.
No.: |
15/149,276 |
Filed: |
May 9, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170322143 A1 |
Nov 9, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N
17/04 (20130101); G01N 17/006 (20130101) |
Current International
Class: |
G01N
17/00 (20060101); G01R 27/02 (20060101); G01N
17/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
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|
|
2 375 235 |
|
Oct 2011 |
|
EP |
|
2 495 082 |
|
Sep 2012 |
|
EP |
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2 150 300 |
|
Jun 1985 |
|
GB |
|
Other References
Extended European Search Report and Opinion issued in connection
with corresponding EP Application No. 17169613.1 dated Oct. 19,
2017. cited by applicant.
|
Primary Examiner: McAndrew; Christopher P
Assistant Examiner: Ferdous; Zannatul
Attorney, Agent or Firm: McNees Wallace & Nurick LLC
Claims
What is claimed is:
1. A corrosion sensor comprising: a metallic plug having at least
one opening; at least one ceramic sheath in the opening of the
metallic plug; and a plurality of probes, each of the plurality of
probes having a central portion with a predetermined cross
sectional area extending from the metallic plug, a first end
extending from the central portion into the ceramic sheath in the
metallic plug, and a second end opposite the first end extending
into the ceramic sheath in the metallic plug; wherein the plurality
of probes are formed of a material selected from the group
consisting of a nickel-based superalloy and a cobalt-based
superalloy; wherein the ceramic sheath electrically isolates the
first end and the second end of each of the plurality of probes
from the metallic plug and the other first ends and second ends;
wherein the plurality of probes are sized to provide a distribution
of predetermined cross sectional areas of the central portions; and
wherein the predetermined cross sectional area of the central
portion of a first probe of the plurality of probes is at least
four times greater than the predetermined cross sectional area of
the central portion of a second probe of the plurality of
probes.
2. The corrosion sensor of claim 1 further comprising at least one
ceramic pack filling a void space between one of the first ends and
the ceramic sheath.
3. The corrosion sensor of claim 1, wherein the plurality of probes
are U-shaped.
4. The corrosion sensor of claim 1, wherein the distribution of
cross sectional areas covers the range of 0.05 mm.sup.2 to 13
mm.sup.2.
5. The corrosion sensor of claim 1, wherein the plurality of probes
include at least five probes.
6. A method of quantifying a corrosion rate of a turbine component,
comprising: measuring a plurality of ohmic resistances across a
plurality of probes of a corrosion sensor in a hot gas path of a
turbine comprising the turbine component during operation of the
turbine, the corrosion sensor comprising: a metallic plug having at
least one opening; at least one ceramic sheath in the opening of
the metallic plug; and the plurality of probes, each of the
plurality of probes having a central portion with a predetermined
cross sectional area extending from the metallic plug, a first end
extending from the central portion into the ceramic sheath in the
metallic plug, and a second end opposite the first end extending
into the ceramic sheath in the metallic plug, the ceramic sheath
electrically isolating the first end and the second end of each of
the plurality of probes from the metallic plug and the other first
ends and second ends, the plurality of probes being sized to
provide a distribution of predetermined cross sectional areas of
the central portions, and the predetermined cross sectional area of
the central portion of a first probe of the plurality of probes
being at least four times greater than the predetermined cross
sectional area of the central portion of a second probe of the
plurality of probes; wherein the plurality of probes are formed of
a material selected from the group consisting of a nickel-based
superalloy and a cobalt-based superalloy; and determining the
corrosion rate by correlating a rate of change in the ohmic
resistance of at least one of the plurality of probes to the
corrosion rate of the at least one of the plurality of probes.
7. The method of claim 6 further comprising locating the plurality
of probes in a hot gas path of the turbine.
8. The method of claim 6 further comprising locating the corrosion
sensor aft of a stage-1 nozzle platform of the turbine.
9. The method of claim 6 further comprising locating the corrosion
sensor in a third stage or a fourth stage of the turbine.
10. The method of claim 6 further comprising adjusting a dosage of
inhibitor supplied to the turbine based on the corrosion rate.
11. The method of claim 6, wherein the measuring and the
determining occur in real time during operation of the turbine.
12. The method of claim 6, wherein the plurality of probes are
U-shaped.
13. The method of claim 6, wherein the distribution of cross
sectional areas covers the range of 0.05 mm.sup.2 to 13
mm.sup.2.
14. A corrosion monitoring system comprising: at least one
corrosion sensor comprising: a metallic plug having at least one
opening; at least one ceramic sheath in the opening of the metallic
plug; and a plurality of probes, each of the plurality of probes
having a central portion with a predetermined cross sectional area
extending from the metallic plug, a first end extending from the
central portion into the ceramic sheath in the metallic plug, and a
second end opposite the first end extending into the ceramic sheath
in the metallic plug, the ceramic sheath electrically isolating
each first end and each second end of the plurality of probes from
the metallic plug and the other first ends and second ends, the
plurality of probes being formed of a material selected from the
group consisting of a nickel-based superalloy and a cobalt-based
superalloy, the plurality of probes being sized to provide a
distribution of predetermined cross sectional areas of the central
portions, and the predetermined cross sectional area of the central
portion of a first probe of the plurality of probes being at least
four times greater than the predetermined cross sectional area of
the central portion of a second probe of the plurality of probes; a
resistance meter measuring an ohmic resistance for at least one of
the plurality of probes; and a computer determining a corrosion
rate by correlating a rate of change of the ohmic resistance to the
corrosion rate of the at least one of the plurality of probes.
15. The corrosion monitoring system of claim 14 further comprising
a display panel displaying the corrosion rate determined by the
computer.
16. The corrosion monitoring system of claim 14, wherein the
plurality of probes are U-shaped.
17. The corrosion monitoring system of claim 14, wherein the
distribution of cross sectional areas covers the range of 0.05
mm.sup.2 to 13 mm.sup.2.
18. The corrosion sensor of claim 1, wherein the predetermined
cross sectional area of the central portion of the first probe of
the plurality of probes is at least sixteen times greater than the
predetermined cross sectional area of the central portion of the
second probe of the plurality of probes.
19. The corrosion sensor of claim 1, wherein the predetermined
cross sectional area of the central portion of the first probe of
the plurality of probes is at least 100 times greater than the
predetermined cross sectional area of the central portion of the
second probe of the plurality of probes.
Description
FIELD OF THE INVENTION
The present disclosure is directed to apparatus, systems, and
methods for monitoring corrosion. More specifically the apparatus,
systems, and methods of the present disclosure monitor corrosion
experienced by turbine components measured as resistance changes
across sensor probes.
BACKGROUND OF THE INVENTION
Modern high-efficiency combustion turbines have firing temperatures
that exceed about 2000.degree. F. (1093.degree. C.), and firing
temperatures continue to increase as demand for more efficient
engines continues. Many components that form the combustor and "hot
gas path" (HGP) turbine sections are directly exposed to aggressive
hot combustion gases, for example, the combustor liner, the
transition duct between the combustion and turbine sections, and
the turbine stationary vanes and rotating blades and surrounding
ring segments. In addition to thermal stresses, these and other
components are also exposed to mechanical stresses and loads that
further wear on the components.
Gas turbine engines may be operated using a number of different
fuels. These fuels are combusted in the combustor section of the
engine at temperatures at or in excess of 2000.degree. F.
(1093.degree. C.), and the gases of combustion are used to rotate
the turbine section of the engine, located aft of the combustor
section of the engine. Power is generated by the rotating turbine
section as energy is extracted from the hot gases of combustion. It
is generally economically beneficial to operate the gas turbine
engines using the most inexpensive fuel supply available. Two of
the more abundant and inexpensive petroleum fuels are crude oil and
heavy fuel oil. One of the reasons that they are economical fuels
is that they are not heavily refined. Not being heavily refined,
they may contain a number of impurities.
Heavy fuel oils typically contain several metallic elemental
contaminants entrained as organic or inorganic complexes. These
metallic elements, which may include one or more of sodium,
potassium, vanadium, lead, and nickel, interact with oxygen and
sulfur during combustion, including oxidation in the combustion
plume, to form reaction products, including low melting point
oxides. Sodium and potassium are conventionally removed prior to
being injected into the combustion chambers by using an upstream
fuel oil treatment system. Elements, such as vanadium and lead,
however, are difficult to remove from the fuel by upstream
accessories means.
Even the more refined liquid fuels used to power gas turbines are
often residuals from distillation processes and typically contain
significant levels of several contaminant elements. The oxides of
these contaminants form low melting point compounds that flux the
protective oxide scales and cause rapid corrosion during
combustion.
The reaction products of these contaminants are problematic for at
least two reasons. First, sodium vanadate, vanadium oxide, sodium
sulfate, potassium sulfate, and lead oxide are extremely corrosive
for the hot gas path alloys, including nickel-based and
cobalt-based superalloys. Second, significant amounts of inhibitors
may be needed to neutralize these corrosive oxides, such as, for
example, inhibitors that form relatively inert vanadates from
vanadium. But it is well known that in spite of the use of
inhibitors, the components still undergo corrosion.
The molten oxides formed from the metal impurities react
aggressively with native oxides formed in the nickel-based and
cobalt-based alloys and induce rapid hot corrosion. Thermal barrier
coatings on the nickel-based and cobalt-based alloys may be used to
try to protect the parts and reduce corrosion, but some molten
oxides, including vanadium oxide, are able to attack and react with
some thermal barrier coatings to remove or degrade the thermal
barrier coatings.
BRIEF DESCRIPTION OF THE INVENTION
In an exemplary embodiment, a corrosion sensor includes a metallic
plug having at least one opening, at least one ceramic sheath in
the opening of the metallic plug, and a plurality of probes. Each
probe has a central portion with a predetermined cross sectional
area extending from the metallic plug, a first end extending from
the central portion into the ceramic sheath in the metallic plug,
and a second end opposite the first end extending into the ceramic
sheath in the metallic plug. The ceramic sheath electrically
isolates each first end and each second end of the probes from the
metallic plug and the other first ends and second ends. The probes
are sized to provide a distribution of predetermined cross
sectional areas of the central portions.
In another exemplary embodiment, a method of quantifying a
corrosion rate of a turbine component includes measuring a
plurality of ohmic resistances across a plurality of probes of a
corrosion sensor during operation of a turbine comprising the
turbine component. The corrosion sensor includes a metallic plug
having at least one opening, at least one ceramic sheath in the
opening of the metallic plug, and a plurality of probes. Each probe
has a central portion with a predetermined cross sectional area
extending from the metallic plug, a first end extending from the
central portion into the ceramic sheath in the metallic plug, and a
second end opposite the first end extending into the ceramic sheath
in the metallic plug. The ceramic sheath electrically isolates each
first end and each second end of the probes from the metallic plug
and the other first ends and second ends. The probes are sized to
provide a distribution of predetermined cross sectional areas of
the central portions. The method also includes determining the
corrosion rate by correlating a rate of change of the ohmic
resistance of at least one of the probes to the corrosion rate of
the probe.
In another exemplary embodiment, a corrosion monitoring system
includes at least one corrosion sensor. The corrosion sensor
includes a metallic plug having at least one opening, at least one
ceramic sheath in the opening of the metallic plug, and a plurality
of probes. Each probe has a central portion with a predetermined
cross sectional area extending from the metallic plug, a first end
extending from the central portion into the ceramic sheath in the
metallic plug, and a second end opposite the first end extending
into the ceramic sheath in the metallic plug. The ceramic sheath
electrically isolates each first end and each second end of the
probes from the metallic plug and the other first ends and second
ends. The probes are sized to provide a distribution of
predetermined cross sectional areas of the central portions. The
corrosion monitoring system also includes a resistance meter
measuring an ohmic resistance for at least one of the plurality of
probes and a computer determining a corrosion rate by correlating a
rate of change in the ohmic resistance to the corrosion rate of the
probe.
Other features and advantages of the present invention will be
apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings, which illustrate, by way of example, the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic partial cross sectional side view of a
corrosion sensor in an embodiment of the present disclosure.
FIG. 2 is a schematic partial cross sectional front view of the
corrosion sensor of FIG. 1.
FIG. 3 is another schematic partial cross sectional view of the
corrosion sensor of FIG. 1.
FIG. 4 is a schematic partial cross sectional view of a corrosion
monitoring system including the corrosion sensor of FIG. 1.
Wherever possible, the same reference numbers will be used
throughout the drawings to represent the same parts.
DETAILED DESCRIPTION OF THE INVENTION
Provided are exemplary systems and methods for measuring the
corrosion experienced by turbine components. Embodiments of the
present disclosure, in comparison to systems and methods not using
one or more of the features described herein, provide a direct
measurement of corrosion in a turbine system, produce corrosion
data assessable by a field service technician, provide a real-time
evaluation of corrosion, permit adjustment of inhibitor dosage
without turbine shut down, or a combination thereof.
One or more specific embodiments of the present invention will be
described below. In an effort to provide a concise description of
these embodiments, all features of an actual implementation may not
be described in the specification. It should be appreciated that in
the development of any such actual implementation, as in any
engineering or design project, numerous implementation-specific
decisions must be made to achieve the developers' specific goals,
such as compliance with system-related and business-related
constraints, which may vary from one implementation to another.
Moreover, it should be appreciated that such a development effort
might be complex and time-consuming, but would nevertheless be a
routine undertaking of design, fabrication, and manufacture for
those of ordinary skill having the benefit of this disclosure.
Specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a basis for the claims
as a representative basis for teaching one skilled in the art to
variously employ the present invention. Any modifications or
variations in the depicted systems and methods, and such further
applications of the principles of the invention as illustrated
herein, as would normally occur to one skilled in the art, are
considered to be within the spirit of this invention.
When introducing elements of various embodiments of the present
invention, the articles "a", "an", "the", and "said" are intended
to mean that there are one or more of the elements. The terms
"comprising", "including", and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements.
Referring to FIG. 1 through FIG. 3, a corrosion monitoring system
includes at least one corrosion sensor 100, including a set of
probes 102 and a metallic plug 104 receiving the probes 102.
Although a set of six probes 102 is shown in FIG. 1, the set may
include any number of probes greater than 1, including, but not
limited to, two, at least two, three, at least three, four, at
least four, five, at least five, six at least six, four to ten, or
five to eight. Each probe 102 preferably has a substantially
constant cross sectional area prior to use that is different from
the cross sectional areas of the other probes 102. Each probe 102
is surrounded by a ceramic sheath 106 to prevent electrical contact
between the probe 102 and the metallic plug 104. A ceramic pack 108
between the probe 102 and the ceramic sheath 106 and/or between the
ceramic sheath 106 and the metallic plug 104 may fill any gaps
while further promoting electrical isolation and holding the
components of the corrosion sensor 100 together. As best seen in
FIG. 2, the probes 102 are substantially U-shaped, more
specifically in the shape of a capital "U", with the two ends
extending into the metallic plug 104.
FIG. 4 shows a corrosion monitoring system 110 including a
corrosion sensor 100 installed in a turbine component 120 of a
turbine. The corrosion monitoring system 110 also includes a
resistance meter 112 in electrical communication with the probes
102 by way of wires 114. The corrosion monitoring system 110
further includes a computer 116 in communication with the
resistance meter 112. The communication line 118 may be a wired
line or a wireless line. The probes 102 extend from the metallic
plug 104 and into the hot gas path (HGP) 122 of the turbine. The
resistance meter 112 measures the electrical resistances of the
probes 102 in situ in real time and determines a corrosion rate
based on changes in the electrical resistances as a function of
time during operation of the turbine.
Hot corrosion is determined based on resistance changes across the
probes 102, with the set of probes 102 being able to measure losses
for different discrete probe 102 diameters, for example, at 25
microns (1 mil), 50 microns (2 mil), 100 microns (4 mils), 250
microns (10 mils), and 500 microns (20 mils).
Although the probes 102 are shown as U-shaped, the probes 102 may
have any contour that exposes a central portion to the HGP 122
while connecting the two ends to an electrical circuit. In some
embodiments, the probes 102 may be contoured based on the clearance
and geometry at the location where the corrosion sensor 100 is
placed. In some embodiments, the central portion is a central
curved portion. In some embodiments, the central portions of the
probes 102 may be substantially straight and parallel to and in
contact with the HGP 122 surface, instead of projecting into the
HGP 122. For instance, each probe 102 may be a layer printed onto a
ceramic sheath 106. The contour of the probe 102 does not affect
the function as long as the cross sectional area is controlled. The
resistance change with loss of cross sectional area due to
corrosion is what creates the desired signal.
In some embodiments, the probes 102 are formed by machining, 3D
metal printing, casting, bending a straight wire, or combinations
thereof. The cross sectional area of the probe 102 may have any
shape as long as the cross sectional area and shape are
substantially unchanged in the central portion of the probe 102
prior to exposure to the HGP 122. In some embodiments, the cross
sectional area of the probe 102 is a circle. In such embodiments,
the cross sectional area may be described in terms of a radius or a
diameter. In other embodiments, the cross sectional area may be
oval, rectangular, or square.
The probes 102 may serve as a corrosion dashboard to dose
inhibitors or pull-out hardware. The design of the corrosion sensor
100 is preferably modular such that the entire unit or individual
probes 102 may be replaced during water washing or maintenance
cycles. In other words, since the effective lifespan of the turbine
or turbine component 120 may exceed the effective lifespan of the
corrosion sensor 100, the spent corrosion sensor 100 is removable
from the turbine component 120 and replaced with a new or working
corrosion sensor 100. In some embodiments, the spent probes 102 are
removable from the metallic plug 104 and replaced with new or
replacement probes 102.
The corrosion sensor 100 includes a metallic plug 104 with at least
one ceramic sheath 106 and a set of probes 102 having a central
portion in the form of U-shaped metallic bends of differing cross
sectional areas made out of the hot gas path alloy of interest. The
metallic plug 104 includes holes for the insertion of the probes
102 having a central portion of different cross sectional areas.
Each of these probes 102 is encapsulated in a ceramic sheath 106 to
maintain electrical insulation from the metallic plug 104. A dense
ceramic pack 108 seals the gaps between the ceramic sheath 106 and
the probes 102 and seals the probe 102 to the metallic plug 104.
Each of these bends of metal is insulated from the others by the
ceramic sheaths 106 in the metallic plug 104.
The ohmic resistance of each of the bends of the probes 102 is
measured continuously as a function of time. This increase is
correlated to the cross sectional area loss of the probe 102, which
in turn is correlated to the corrosion rate. The ohmic resistance
may be measured by applying a predetermined voltage to each probe
102 and measuring the resulting current or by applying a
predetermined current to each probe 102 and measuring the resulting
voltage. The initial reading calibrates the system, taking into
account the temperature component of the resistance. As the probes
102 thin due to corrosion, the resistance increases. The measured
increase in resistance is calibrated to the cross sectional area
loss of the probe 102, which in turn is converted to a corrosion
rate.
A set of probes 102 with progressively greater cross sectional area
provides a corrosion sensor 100 that continuously monitors
corrosion rate of the HGP 122 hardware. The smallest cross
sectional area probe 102 initially provides the most sensitive
measure of corrosion. As the exposure of the corrosion sensor 100
to corrosion increases, the cross sectional area of each probe 102
decreases and the ohmic resistance increases. The measured increase
in ohmic resistance is correlated to the cross sectional area loss
of the probe 102, which in turn is correlated to the corrosion
rate. When the cross sectional area of the smallest probe 102
becomes too small to provide a reliable resistance reading, the
next smallest cross sectional area probe 102 has a decreased cross
sectional area similar to the initial cross sectional area of the
smallest cross sectional area probe 102 and therefore serves as the
most sensitive probe 102 of the corrosion sensor 100 until it, too,
has a cross sectional area too small to provide a reliable
resistance reading. Thus, the set of probes 102 having
progressively increasing cross sectional areas increases the useful
life of the corrosion sensor 100. The probe 102 with the largest
cross sectional area may serve as a corrosion odometer by
reflecting the total amount of corrosion that has occurred since
the corrosion sensor 100 was installed. Such a corrosion sensor 100
may be used both as a life odometer and as a feedback indicator to
adjust the dosage of inhibitors being supplied in real time based
on assessed corrosion rates.
The series of probes 102 with progressively higher cross sectional
areas permits development of a corrosion sensor 100 that
continuously monitors the corrosion rate of the HGP 122 hardware in
real time. Such a device is very sensitive. A 250-micron diameter
(0.049 mm.sup.2) cross sectional area) probe 102, for example,
shows a 50% increase in resistance for a 20% reduction in diameter,
which corresponds to a loss of the outer 25 micron (1 mil) layer
thickness of the probe 102 as corrosion loss. If the next probe 102
has a diameter of 500 microns (20 mils), a 50% increase in
resistance corresponds to a 100-micron decrease in diameter. With
six probes 102 starting from 250 microns (10 mils) in diameter to 4
mm (160 mils) in diameter, corrosion amounts may be monitored all
the way from 25 microns (1 mil) to 500 microns (20 mils). For
example, the diameters of the six probes 102 may be 250 microns (10
mils), 500 microns (20 mils), 1 mm (40 mils), 2 mm (80 mils), 3 mm
(120 mils), and 4 mm (160 mils) such that the cross sectional areas
of the probes 102 cover the range of about 0.05 mm.sup.2 to about
13 mm.sup.2. Alternatively, cross sectional areas may cover the
range of about 0.01 mm.sup.2 to about 100 mm.sup.2, about 0.02
mm.sup.2 to about 50 mm.sup.2, about 0.04 mm.sup.2 to about 25
mm.sup.2, about 0.1 mm.sup.2 to about 10 mm.sup.2, or any range or
sub-range therebetween.
The probes 102 having a central portion may be inserted through
borescope plugs at the stage-1 and stage-3 locations of the turbine
to monitor both type-1 and type-2 corrosion. Type-1 corrosion, as
used herein, refers to hot corrosion that typically occurs in the
temperature range of 850 to 950.degree. C. (1560 to 1740.degree.
F.) starting with the condensation of fused alkali metal salts on
the component surface. Type-2 corrosion, as used herein, refers to
hot corrosion that typically occurs in the temperature range of 650
to 800.degree. C. (1200 to 1470.degree. F.) resulting from
formation of low melting point mixtures (typically Na.sub.2SO.sub.4
and CoSO.sub.4/NiSO.sub.4).
Since the measured resistance change is caused by the cross
sectional area change of the probe 102, the corrosion monitoring
system 110 may measure a corrosion rate that is cumulative of
multiple types of corrosion. The monitored corrosion rate is
preferably not dependent on what mechanism or mechanisms are
causing the corrosion to the probe 102.
The corrosion data may be interfaced through Mark VI or Mark VIe
controllers (General Electric Company, Fairfield, Conn.) and
independent control systems to adjust for inhibitor dosage and to
make decisions on when to shut down the system for a more detailed
inspection of the hardware.
In some embodiments, the corrosion sensors 100 are placed in at
least two locations in the turbine to measure corrosion in
different stages of the turbine. At least one corrosion sensor 100
may be placed aft of the stage-1 nozzle platform toward the casing
side to measure corrosion events at close to the firing
temperature. The sacrificial probes 102 may have the same base
material and coating as what is used in the turbine. In some
embodiments, three corrosion sensors 100 are placed along the
circumference aft of the stage-1 nozzle platform.
Additionally, at least one corrosion sensor 100 may be placed close
to the stage-3 or stage-4 nozzles, as appropriate, to capture the
corrosion effects associated with both type-2 corrosion and with
vanadium oxide being in the liquid state. Corrosion at this
location is severe, if the inhibitor dosage is not right. In some
embodiments, the dosage of the inhibitor is adjusted and the
corrosion rate is monitored in real time in a feedback loop to
optimize inhibitor dosage while minimizing the corrosion rate.
The resistivity measurements are preferably done from outside the
casing and the outputs are hardwired to a dashboard that could be
placed along with the Mark VI or Mark VIe control panel. In some
embodiments, the corrosion sensor 100 from the hot section and the
corrosion sensor 100 from the compressor inlet, if both deployed,
are displayed together. A display panel, which is
environment-related, captures corrosion events in the cold and hot
sections of the turbine.
While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *